The present invention relates in general to slack adjuster assemblies which automatically adjust the slack in the brake rigging of a railway vehicle and, more particularly, the invention relates to a double-acting compression actuable slack adjuster assembly which adjusts the slack in such brake rigging driving each brake application. For a number of years, slack adjusters have been provided in the brake rigging of railway vehicles to automatically adjust the slack in such brake rigging for a number of reasons. One such reason of significance is that the slack adjuster maintains the brake cylinder piston rod travel within a preselected travel distance automatically. Maintaining such brake cylinder piston rod travel distance within the prescribed limit is of particular importance in present day higher speed train operations. In addition, today's trains have a greater number of cars due to better locomotive equipment. For these reasons, it is important that the piston rod travel of the brake cylinder be maintained at a relatively close tolerance in order to properly balance the fluid pressure, usually air, in the fluid cylinder with that in the reservoir. If this were not the case, a car with a long piston rod travel would be operating at a reduced pressure and also at a time lag with respect to other cars in the train makeup that had a proper piston rod travel. On the other hand, a car with a piston rod travel that is too short would be operating at a higher cylinder fluid pressure and at an advanced timing with respect to the other cars exhibiting a proper piston rod travel. Either of the above conditions is undesirable. The above considerations also must be taken into account with respect to the supply of fluid.
Another important reason is that the slack adjusters will provide a substantially more uniform braking force to be applied to each set of wheels on each car making up a train. Because of the improvement in providing a more uniform braking force, the undesirable possibility of some cars in the train being held back while other cars roll ahead is generally minimized.
More recently and of significance in the fact that a slack adjuster has been increasingly used to replace one of the brake cylinders on those railroad cars equipped with truck mounted brake rigging. Due to the elimination of one brake cylinder, in this application considerable cost and desirable weight saving advantages can be achieved. However, the linkages required are generally more complex because the slack adjuster assembly becomes a force transmitting member in such brake riggings. This application for a slack adjuster assembly, however, requires an even greater reliability for a number of obvious reasons.